Nanosensors are a technology that may exist in the future. The closest thing in existence to these currently are MEMS (Micro Electro Mechanical Systems) devices. A MEMS biosensor may be based upon a thin film bulk acoustic wave resonator, with some components of it less than 100nm. They work in a similar way to Quartz Crystal Microbalances, but at much high frequencies, 3GHz and beyond. They have been fabricated by the famous biological nanotechnologist Dr. Gregory Ashley at Cranfield University as part of his doctoral thesis.